An F-22A Raptor being flown on a test mission from Edwards Air Force Base, Calif., crashed Wednesday morning, March 25, about 35 miles northeast of the California desert base, the Air Force said.

The Air Force was trying to determine what caused the crash of the $142 million stealth fighter. The fate of the pilot, the only person aboard, was not known, said Maj. David Small, an Air Force spokesman at the Pentagon.

A board of officers is to investigate the accident. It is the second time that an F-22 has crashed. The first one was during the aircraft's test and evaluation period in December 2004, also at Edwards, when the pilot was able to eject safely, the Air Force said.

The F-22A acquisition program is managed by the Aeronautical Systems Center at Wright-Patterson Air Force Base. The Air Force has 134 of the fighters in its inventory.

Defense Secretary Robert Gates and Air Force leadership have had differences over how many F-22s should be purchased for the future. The Air Force says it is needed to modernize its attack fleet, and that its combination of sensor systems, integrated electronics and weapons makes it capable of tracking and shooting down enemy aircraft before it can be detected. Gates has questioned, however, how effective the F-22 would be for fighting in places like Afghanistan.

The Air Force has flown the F-22 for crowds at the Vectren Dayton Air Show. The plane is assembled at Lockheed Martin Corp.'s plant in Marietta, Ga.